cc: Don't infinitely throttle large raster tasks

cc/resources/pixel_buffer_raster_worker_pool.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/resources/pixel_buffer_raster_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/containers/stack_container.h"
 #include "base/debug/trace_event.h"
@@ skipping 497 matching lines @@
     RasterTaskState& state = *state_it;
 
     // Skip task if completed.
     if (state.type == RasterTaskState::COMPLETED) {
       DCHECK(std::find(completed_raster_tasks_.begin(),
                        completed_raster_tasks_.end(),
                        task) != completed_raster_tasks_.end());
       continue;
     }
 
-    // All raster tasks need to be throttled by bytes of pending uploads.
+    // All raster tasks need to be throttled by bytes of pending uploads,
+    // but if it's the first task allow it to complete no matter what its size,

[reveman, 2014/08/21 01:15:47]

nit: maybe "only" instead of "first" as this is effected by previously scheduled
tasks and not only the tasks being scheduled at this time

[enne (OOO), 2014/08/21 01:34:15]

Done.

+    // to prevent starvation of the task queue.
     size_t new_bytes_pending_upload = bytes_pending_upload;
     new_bytes_pending_upload += task->resource()->bytes();
-    if (new_bytes_pending_upload > max_bytes_pending_upload_) {
+    if (new_bytes_pending_upload > max_bytes_pending_upload_ &&
+        bytes_pending_upload > 0) {

[reveman, 2014/08/21 01:15:47]

nit: s/bytes_pending_upload > 0/bytes_pending_upload/

[enne (OOO), 2014/08/21 01:34:15]

Done.

       did_throttle_raster_tasks = true;
       if (item.required_for_activation)
         did_throttle_raster_tasks_required_for_activation = true;
       continue;
     }
 
     // If raster has finished, just update |bytes_pending_upload|.
     if (state.type == RasterTaskState::UPLOADING) {
       DCHECK(!task->HasCompleted());
       bytes_pending_upload = new_bytes_pending_upload;
@@ skipping 220 matching lines @@
 void PixelBufferRasterWorkerPool::ThrottleStateAsValueInto(
     base::debug::TracedValue* throttle_state) const {
   throttle_state->SetInteger("bytes_available_for_upload",
                              max_bytes_pending_upload_ - bytes_pending_upload_);
   throttle_state->SetInteger("bytes_pending_upload", bytes_pending_upload_);
   throttle_state->SetInteger("scheduled_raster_task_count",
                              scheduled_raster_task_count_);
 }
 
 }  // namespace cc